Identification of Zn-Bearing Micas and Clays from the Cristal and Mina Grande Zinc Deposits (Bongará Province, Amazonas Region, Northern Peru)

Abstract

Zn-bearing phyllosilicates are common minerals in nonsulfide Zn deposits, but they seldom represent the prevailing economic species. However, even though the presence of Zn-bearing clays is considered as a disadvantage in mineral processing, their characteristics can give crucial information on the genesis of the oxidized mineralization. This research has been carried out on the Mina Grande and Cristal Zn-sulfide/nonsulfide deposits, which occur in the Bongará district (Northern Peru). In both of the deposits, Zn-bearing micas and clays occur as an accessory to the ore minerals. The XRD analyses and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) investigations revealed that the Zn-bearing micas that are occurring in both deposits mostly consist of I/S mixed layers of detrital origin, which have been partly altered or overprinted by sauconite during the supergene alteration of sulfides. Sporadic hendricksite was also identified in the Cristal nonsulfide mineral assemblage, whereas at Mina Grande, the fraipontite-zaccagnaite (3R-polytype) association was detected. The identified zaccagnaite polytype suggests that both fraipontite and zaccagnaite are genetically related to weathering processes. The hendricksite detected at Cristal is a product of hydrothermal alteration, which is formed during the emplacement of sulfides. The complex nature of the identified phyllosilicates may be considered as evidence of the multiple processes (hydrothermal and supergene) that occurred in the Bongará district.

Mineral characterisation of the non-sulphide Zn mineralisation of the Florida Canyon deposit, Bongará District, Northern Peru

“…Table 3. Summary comparison of Zn supergene deposits data from the Bongará District, Northern Peru, with the Florida Canyon, Mina Grande (Arfè et al 2017a(Arfè et al , 2017b and Cristal deposits (Arfè et al 2018;Mondillo et al 2018a).…”

“…Previous research in this area, such as Reid (2001), Basuki et al (2008) and Basuki and Spooner (2009), focused on the primary MVT sulphide mineralisation within the Florida Canyon deposit. The Pucará Group hosts other MVT Zn–Pb deposits, such as San Vicente (Fontbote and Gorzawski 1990; Spangenberg et al 1996, 1999) and Shalipayco (Moritz et al 1996) and supergene non-sulphide Zn deposits, such as Mina Grande (Arfè et al 2017a, 2017b) and Cristal (Arfè et al 2018; Mondillo et al 2018a, 2018b).

Figure 1 Location of the Florida Canyon deposit in northern Peru.

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Dissolution Properties of a Dolomite Containing Zinc Ore in Sodium Hydroxide Solutions

“…The difference between 100% zinc dissolution efficiency and dissolution efficiencies obtained in NaOH and HCl solutions probably be caused by the presence of zinc, other than in smithsonite, in structures of minerals of ore sample having some resistance to dissolution both in alkaline and acid solutions, i.e. zinc containing dolomite, clay minerals, goethite and calcite, as also indicated in the related literature (Whittaker and Żabiński, 1981;Rosenberg and Champness, 1989;Borg et al, 2003;Boni et al, 2009a,b;Coppola et al, 2009;Mondillo et al, 2011;Boni et al, 2013;Mondillo et al, 2014;Santoro et al, 2014;Mondillo et al, 2015;Paradis et al, 2015;Choulet et al, 2016;Arfè et al, 2017;Balassone et al, 2017).…”

Zn-clays in the Kihabe and Nxuu prospects (Aha Hills, Botswana): A XRD and TEM study

“…Notable examples of fraipontite are the occurrences in Belgium (Coppola et al 2008), in the Bongará ore district, Peru (Arfè et al 2017;Balassone et al 2020) and in the Bou Arhous deposit, Morocco (Buatier et al 2016;Choulet et al 2016). In the Bongará district, fraipontite is present as a chemically and mineralogically homogenous phase in the form of late and well-crystallized pore-infills within previously formed clays (Balassone et al 2020).…”

“…Furthermore, the dissolution of aluminosilicates from siliciclastic rocks during the ore-formation process can result in the formation of various clay minerals, which may behave as effective sinks for valuable metals as Zn and Cu (Boni and Mondillo 2015 and references therein). Consequently, the occurrence of Zn-clays, either as subordinate phases (e.g., La Calamine, Belgium; Bou Arhous, Marocco; Bongarà, Perù; Coppola et al 2008;Choulet et al 2016;Balassone et al 2020) or as prevailing ore minerals (e.g., Accha-Yanque, Peru; Skorpion, Namibia; Borg et al 2003;Mondillo et al 2015;Balassone et al 2017), has been documented in several research Moroccan High Atlas (Buatier et al 2016;Choulet et al 2016) and in the Bongarà (Perù) mining districts (Arfè et al 2017;Balassone et al 2021). In both cases its formation was explained by a direct precipitation process from hydrothermal to supergene metals-rich solutions;…”